This invention relates to a picking control device in a loom in which in an air jet loom, even when the flying characteristic of weft yarn is varied, stable picking operation can be continued.
In the air jet loom, when the flying characteristic of weft yarn used for weaving is varied, picking sometimes becomes unstable. It is considered that such unstable picking as just mentioned principally results from change in air resistance of yarns since yarn properties such as coarseness of yarns, sizes of fuzz and the like are varied lengthwise of weft yarn.
In view of the above, various procedures have been proposed in an attempt of continuing the stable picking operation even when the flying characteristic of weft yarn is varied. The most typical procedure is designed so as to monitor a loom mechanical angle (hereinafter referred to as "arrival angle") wherein in picking, an end of weft yarn arrives at the anti-picking side, and controls a loom mechanical angle (hereinafter referred to as "start angle") for starting the picking operation and jet pressure of picking main nozzle and sub-nozzle.
In the aforementioned method, when the flying characteristic of weft yarn lowers so that the lagging of the arrival angle is detected, a control is made so as to make fast the picking start angle and increase the jet pressure in order to correct the lagging of the arrival angle. On the other hand, with respect to the leading of the arrival angle, the picking start angle is retarded and the jet pressure is decreased to thereby maintain the arrival angle constant whereby a better result can be obtained, than the case where only one of the start angle and jet pressure comprises an object to be controlled.
A further proposal is that an upper limit value is set to the jet pressure, and only when the jet pressure controlled by a deviation of the arrival angle exceeds the upper limit value, a control is made so that the start angle is held fast (Japanese Patent Laid-open No. 2 (1990)-118138 publication).
Incidentally, generally, when the jet pressure is excessively low, unevenness of the deviation of the arrival angle for each picking increases, and as a result, the flying of the weft yarn becomes unstable and a weft stop is apt to occur. Conversely, when the jet pressure is excessively high, at the time of termination of picking, a so-called cutting of the weft yarn at the time of termination of picking is apt to occur as well as occurrence of fuzz stripes on the fabrics and in addition, air consumption is excessively large, which is uneconomical. Accordingly, it is desired that the optimum value of the jet pressure be set to a low value at which no weft stop occurs.
On the other hand, when the start angle is excessively fast, the warp shedding is not sufficiently formed and weft engagement is apt to occur but it is advantageous that the start angle is as fast as possible in view of securing the sufficient flying time of weft yarn. The optimum value is present in the case where the start angle is fast in consideration of the above matter.
That is, the jet pressure and the start angle are advantageously as close as possible to these optimum values, reducing occurrence of inferior weaving such as restriction cutting, weft engagement with warp yarn and the like. Thus stable operation can be continued.
However, employment of the aforementioned prior art poses a problem in that it is difficult to coincide the jet pressure and the start angle with the optimum value and the stable operation cannot be continued with a sufficient scope. That is, in the case where correction signals (i.e., based upon a fast or slow arrival angle); are merely applied in parallel to control systems for controlling the start angle and the jet pressure or when one exceeds the upper limit value, a correction signal is applied to the other, such that stable picking could be realized, however the jet pressure and the start angle at that time are possibly greatly shifted from the respective optimum values since no means are provided for setting them to the optimum value. In other words, the operation is sometimes continued in the state where the jet pressure and the start angle are greatly deviated from the respective optimum values, at which time a scope for achieving the stable picking is small, and most likely, air consumption unreasonably increases.